Search for an imp inside a cave at the entrance of Darkwhisper Gorge in southern Winterspring, purchase a Fel Elemental Rod and return to Mux Manascrambler in Gadgetzan.
The core will provide us with enough juice to power our device; now we just have to build a rod that can channel that energy without melting.
I met an imp in Winterspring that sold all manner of exotic goods. He had an elemental rod that would do perfectly. I'm kicking myself in the head right now for not having bought it.
He lives inside a cave in the entrance to Darkwhisper Gorge. Sneak in there and try to find him.
Make sure he only charges you forty gold; that's the price he quoted me!